What caused the resurgence of AI since the early 2000s?
To vastly oversimplify a lot of the progress of modern research in AI/neural nets, the recent advances stems from applicational improvements of the back propagation algorithm. 

ex: our recent possession of big data (it turns out that back-prop works very well if you have lots of data to feed into the network), increased computing power to harness that data, and creative network designs to leverage that computing power (deep learning).

So far I haven't found a good source that integrates the knowledge of current practice of neural networks into the classical study of AI nicely. But if you are still interested you can read this modern classic textbook on neural networks and make your own judgements. 

http://www.deeplearningbook.org